What a great thread! One of my fav MJ harmonies is def Leave Me Alone! Those harmonies are insane. It comes in from everywhere, right, left, vertical, horizontal lol.
Btw im suprised no one has mentioned the harmonies michael does in the demo of The Girl Is Mine. You know the '' aahhh, aahhh '' that he does in the begining and the end. So soothing yet powerful!